Radio apparatus



/NvENToRs 'l HERBERT H. HuLsE JOHN l. BELLAMY RaUNEY G. RICHARDSON LAUEENCE'J. LEsH A 1 @n m um R\ WN 4 Wm.) wm.; A QN 0 Mm w L. m\ RIA Q m D u j A M .Ww ww .....J MN WN .Q wn F u L. f S N Nn QN J1 R rl hln. Ille 5 n A m @l mm H 7 c a N m. A w A ,i A Q F Ww n Nw a i V, L H. W. m A M E w. f .R f... y d p ric. RADiANJTN Examinalf July 9, 1935. H. H. HULsE Erm.

RADIO APPARATUS Filed July 11, 1930 4 Sheets-Sheet 2 W wm r W .M 1,1. n SPM. H H q QW Q q RODNEY G. RlcHARDsaN LAURENCE J. LEsH txammr 45o. RAQL'S'T E NBGY- a July 9, 1935- H. H. HuLsE Erm.

RADIO APPARATUS Filed July 11, 1930 .QQ n@ @Y IN VENTORS HERBERT H. HuLsE JOHN l. BELLAMY RoDNEv G. RICHARDSON LAURENCE J. LEsH ...wm ...Mm vM Examiner 5.25m RADMNGY July 9, 1935. H. H. HuLsr: E1- Al.

RADIO APPARATUS w E SH s 4 nvm... t suMAL e MHAHJ. e ...Lw h HL E S N ERC ETBGN .ml WM/.YE .W L M2M h EHNA s HDD]- 4 SN Jon, MQ 0 MQ 3 wQN L 1 v. 1 u J w F ATTY Patented `luly 9, 1935 UNITED STATES PATENT OFFICE RADIO APPARATUS Herbert H. Hulse, Chicago, and John I. Bellamy, Brookeld, and Rodney G. Richardson and Laurence J. Lesh, Chicago, Ill., assignors, by mesne assignments, to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application July 11, 1930, Serial N0. 467,192

25 Claims.

The present invention relates in general to radio apparatus and more particularly to a system of radio program service and remote control of radio receiving sets. The main object of the invention is the provision of a complete radio service system which is especially adapted for use in hotels, apartment buildings, etc. to furnish radio service to the guests or tenants of such establishments.

Accordingvto one feature of the invention, subscribers to the service may have access to a number of permanently tuned radio sets for program service and they may also have access to a number of special receiving sets which are arranged to be remotely controlled from the hotel rooms or apartments.

Another feature of the invention relates to the arrangement whereby the entire system may be supervised and controlled from a central switchboard preferably located in the oce of the hotel or apartment building.

According to one feature of the invention a special receiving set which has been taken for use may be tuned to any desired station by means of a dial in the hotel room, and the loudness or volume may also be controlled by means of the dial.

A particular feature of the invention is the new and improved circuit arrangement for a tuning switch which is set under control of the dial to tune a radio receiving set to respond to any desired broadcasting station. This specific switch structure is disclosed and claimed in application Serial No. 573,864, led November 9, 1931.

A clear understanding of the above and other features of the invention may best be had from the following detailed specification when read in connection with the accompanying drawings comprising Figs. 1 to 7, inclusive, in which Figs. 1, 2 and 3 show by means of the usual schematic diagram the circuit connections for a radio service system in accordance with the present invention,

Fig. 4 is a plan view of the improved tuning switch TS of Fig. 3,

Fig. 5 is an end view of the switch TS, and

Figs. 6 and 7 show the auxiliary condensers which are incorporated in the tuning switch TS.

Figs. l, 2 and 3 of the drawings, when Fig. 2 is placed to the right of Fig. 1 and Fig. 3 is placed directly above Fig. 2, show a complete layout of the system in accordance with the present invention. Assuming that-the system is installed in a hotel, each guest room in the hotel may be equipped with a. wall jack, such as 6, shown in Fig. 1 of the drawings and all of the jacks may be cabled to a central switchboard in the office of the hotel and will terminate at the switchboard in a regular line jack, such as is used on telephone switchboards. The switchboard may be provided with a jack for each room in the hotel. A number of selecting switches, such as SS in Fig. 1, may be mounted on a suitable mounting frame near the control switchboard and the incoming line conductors to these switches are connected to connecting plugs at the switchboard. A supervisory lamp, such as 9, and a key, such as K, is associated with each switch and mounted on the control switchboard with the connecting plug. The mechanical structure and the driving mechanism of the switch SS is similar to the well known rotary line-switch common in automatic telephony but the circuits have been considerably revised in order to perform various functions as will be pointed out in the detailed description of the operation of the system.

The switches, such as SS, have access in the switch banks to a number of permanently tuned radio receiving sets, such as 44 shown in Fig. 1, and also to a number of special radio sets and associated tuning switches, such as disclosed in Figs. 2 and 3 of the drawings. In the particular embodiment disclosed, nine permanently tuned radio receiving sets may be provided each of which is tuned to respond to a particular broadcasting station. The dialling of any digit from 1 to 9 operates the switch, such as SS, to the corresponding bank contacts to pick out the desired radio program. In case the digit 0 is dialled, the selecting switch SS automatically hunts for an idle radio set, such as disclosed in Figs. 2 and 3 of the drawings. The key K which is located on the control switchboard may be used to limit subscribers to either one or the other of these services. The supervisory lamp 9 is lighted whenever the associated selecting switch SS is engaged. The banks of the selecting switch, such as SS, are multipled to the corresponding banks of all other selecting switches.

Fig. 2 of the drawings shows the controlling apparatus for the tuning switch associated with each of the special radio receiving sets. The electron tube 55 and the relays 5|, 51, 6I, 68 and 1| are provided to control the setting and release of the register switches and volume control switches T, U, VI and V2. These switches are similar in construction to the well known minor switch used in automatic telephony but have their circuits especially arranged to perform various functions that vwill be pointed out in the detailed explanation of the operation. The switches T and U are used to mark the bank contacts of the tuning switch TS for tuning the radio receiving set to respond to the desired broadcasting station. The switches V| and V2 are provided to allow the volume of the receiving set to be automatically controlled by means of the dial in the subscribers room. The antenna of the radio receiving set is indicated at |08.

Fig. 3 of the drawings shows the radio receiving set RR and the tuning switch TS. The radio receiving set RR forms no part of this invention and may be any one of a number of well known makes. However, the main tuning condensers 2|0, 2|| and 2|2 which are usually controlled by means of tuning dials on the front of the set are in this case a part of the tuning switch TS and the movable plates of these condensers are mounted on the switch shaft along with the wipers |31 to |42, inclusive. The mechanical structure of this switch is shown in Figs. 4 to '1, inclusive, of the drawings. The tuning switch TS operates on the well known iinder principle, that is, when the start lead ||4 is grounded the switch automatically rotates until the wipers |31 and |38 engage bank contacts which have been marked by the register switches T and U of Fig. 2. The auxiliary condensers, such as |59, |60 and I6 I, form a part of the switch banks and the detailed construction of these auxiliary 'condensers is shown in Figs. 4, 6 and 7 of the drawings.

The tuning switch is shown in Figs. 4 to 1, inclusive, of the drawings. The switch consists of two angle mounting brackets, 200 and 20|, upon which the switch banks and the stationary plates of the condensers are mounted. At the ends of these brackets are the strips 202 and 203 which serve as bearings for the shaft 204. Upon the two angle mounting brackets 200 and 20| are mounted the switch banks 225, 226, 221, 228, 229 and 230 and the stationary sections of the main tuning condensers 2 I0, 2| and 2|2.

Connections to the stationary sections of the main tuning condensers 2|0 to 2|2, inclusive, are made by means of terminals 23|, 232 and 233. The ground connection to the movable sections of these condensers is made by means of terminal 234 and through the shaft of the switch.

At one end of the switch is mounted the driving magnet |33 with its armature 2 I 5 and driving pawl 205. The shaft 204 is rotatably suspended in bearings in the end pieces 202 and 203 and mounts the wipers |31 to |42 (Fig. 3) of the switch and also the movable sections of the main tuning condensers 2|0, 2|| and 2|2. Mounted at one end of the shaft in a position so that its teeth will be engaged by the driving pawl 206 is the driving ratchet wheel 205. The holding and centering arrangement consists of a wheel 201 having indentations in its periphery in the form of a sine wave. These indentations are adapted to be engaged by the roller 209 which is held in position by the spring 208. 'Ihe spring 208 is very stilly tensioned so that the roller 209 will be forced to the bottom of the depression in the periphery of the wheel 201 thereby exactly centering the wipers and condensers of the switch in` each of its positions to provide sharp tuning of the radio set at each position of the switch.

The three banks 228 to 230, inclusive, engaged by wipers |39, |40 and |4l, respectively, are provided with auxiliary tuning condensers as shown in Figs. 4, 6 and '7 of the drawings. The outer respect to the bank contacts by means of the adjusting screws, such as 2|1. Insulating blocks 222 and 223 are provided to provide proper spacing between the elements of the bank, and the complete assembly is held in position by means of the clamping screws, such as 22|. This common element of the auxiliary condensers is provided with a terminal and all three of these elements are connected together to one terminal of the filament battery as shown in the circuit diagram of Fig. 3.

The main tuning condensers, such as 2|0, 2|I and 2I2, are straight line condensers so that the change in capacity will be proportional to the amount of rotation irrespective of the position of the condensers.

The switch illustrated has twenty-live positions and, therefore, provides for tuning the associated radio receiving set to any one of twenty-iive different broadcasting stations. The size of the switch may be increased so as to provide any number of positions up to one-hundred, thereby allowing the radio set to be tuned to any one of the assigned broadcasting channels.

Each broadcasting channel is assigned a call number such that the operation of the switch to the position corresponding to the call number will rotate the main tuning condensers 2|0 to |2, inclusive, to positions which will approximately tune the radio set to respond to the particular broadcasting channel. The three auxiliary condensers associated with the bank contacts on which wipers |39 to |4I, inclusive, are resting are then separately adjusted until the set is exactly tuned to respond to the desired channel. The same procedure is followed for each position of the tuning switch. All the auxiliary condensers are adjusted in this manner when the system is installed and thereafter the operation of the tuning switch to the position corresponding to the call number of the desired broadcasting station will exactly tune the radio set to respond to the frequency of the desired station.

Having given a general description of the arrangement of the radio service system and having described the details of construction of the tuning switch TS, a detailed description of the operation of the system will now be given.

Referring now in detail to Figs. 1 to 3, inclusive, the keys, such as K, and lamps, suchas 9, associated with each of the selecting switches SS, and the plugs, such as 8, -which terminate these switches are preferably located at a central switchboard which also contains a switch jack, such as 1, for each room in the hotel. A supervisory lamp, such as 43 in Fig. 1, is associated with each of the permanently tuned radio sets, such as 44, and these lamps are also located on the switchboard so that the clerk can tell by the lamps which of the permanently tuned radio sets are in use. In a hotel of about five-hundred rooms probably about one-hundred selecting switches, such as SS, would prove sufficient since all of the rooms would not be occupied at the same time and al1 of the guests would not wish to subscribe for the radio service.

It will be assumed that a guest of the hotel has just registered and engaged a room and that he desires the radio service. When the hotel clerk assigns the room he selects an idle plug, such as 8, which is associated with an idle selecting switch and inserts this plug in the switch jack 1 associated with the assigned room. A loud speaker, such as LS, and the associated dial and keys is then taken to the room and the plug 5 associated with the speaker is inserted in the Wall jack 6. The apparatus is now in readiness for the guest to avail himself of the radio service.

A card of instructions may be furnished with the loud speaker containing a list of the permanently tuned radio receiving sets for the program service and also a list of numbers to be dialled in case one of the special radio receiving sets is to be employed to select any one of a large number of radio broadcasting stations. In the system shown, any digit from 1 to 9, inclusive, will select any one of nine permanently tuned radio receiving sets for program service. If the digit 0 is dialed the selecting switch SS will automatically hunt for an idle radio set which may be controlled by means of the dial and tuned to any one of a large number of stations.

It will be assumed that the guest wishes to listen to a program from a particular broadcasting station, such as WGN, and that upon consulting the list furnished with his loud speaker he finds that dialling the digit l will extend his line to the permanently tuned radio receiving set which is tuned to respond to the desired station. He thereupon depresses the key R, which is mounted on a base with the loud speaker LS and proceeds to dial the digit l.

As soon as the key R is depressed a circuit is completed for the line relay Ill of the selecting switch SS which extends from ground, upper winding of relay I0 back contact of armature 21 and said armature, tip of plug 8, spring of jack 1, spring of jack 6, sleeve of plug 5, contact of the special release key SR, winding of the impedance coil I, contacts of dial D, contacts of the release key R, tip of plug 5, spring of jack 6, spring of jack 1, sleeve of plug 8, armature 30 and its back contact, lower winding of relay I0 to battery. Line relay Ill operates in this circuit and at armature I5 and its front contact closes a circuit for the release relay I I which extends from ground, back contact of armature 28 and said armature, armature I5 and its front contact, winding of release relay I I and associated resistance in multiple, normally closed contacts controlled by armature I8, normal bank contact 39 of wiper 31, wiper 31, back contact of armature 22 and said armature, inter-v rupter contact 34 of the rotary magnet, winding of rotary magnet 33 to battery. Release relay I I operates in this circuit and at armature I6 and its back contact opens one homing circuit of the switch and at armature I1 and its back contact opens the other homing circuit of the switch. At armature I8 and its front contact direct battery is connected to the lower terminal of the release relay so that this relay will not release when the switch steps off-normal. At armature I9 and its front contact a circuit is closed for the supervisory lamp 9. A point in the impulsing circuit to the rotary magnet 33is completed at armature I1 and its front contact.

When the digit 1 is dialled the springs of dialD are opened once thereby momentarily interrupting the circuit of the line relay IIJ. Line relay I0 mail# momentarily releases, thereby sending an impulse from ground at the back contact of armature 28, armature I5 and its back contact, armature I1 and its front contact, winding of series relay I2, winding of the rotary magnet 33, to battery. The rotary magnet 33 momentarily energizes and upon releasing at the end of the impulse, steps the wipers of the switch into engagement with the iirst bank contacts. Series relay I2 energizes in series with the rotary magnet and at armature 22 and its back contact opens a point in the energizing circuit of switching relay I3. The series relay I2 is provided with a copper sleeve which makes it slow acting, and it therefore remains energized for a short time after the impulses cease. Since the digit 1 was dialled, no more impulses are transmitted to the rotary magnet and the series relay I2 releases after a short interval. The closing of armature 22 and its back contact completes a circuit for the switching relay I3 extending from ground, winding of relay I3, contact 24 of key K, the second bank contact engaged by wiper 31 and said wiper, back contact of armature 22 and said armature, interrupter spring 34 of the rotary magnet, winding of rotary magnet 33, to battery. Switchingrelay I3 operates in this circuit but due to the high resistance of this relay the rotary magnet 33 does not energize. Relay I3 upon operating closes armatures 23 and 26 and their front contacts, thereby completing the circuit from the loud speaker in the hotel room to the speaker leads extending from the permanently tuned radio receiving set 44 over condensers 3|l and 32 and wipers 38 and 35 and the second bank contacts of the selecting switch SS.

In case another subscriber or guest is listening to the program from the receiving set 44, the relay 40 will be operated and the calling subscriber will immediately receive the program at his loud speaker.

Assuming that no other guest is listening to the program from set 44, the relay 40 is not operated and when relay I2 releases at the end of the impulse train a circuit is closed from battery, windi ing of rotary magnet 33, interrupter springs 34, armature 2l and its back contact, armature 20 and its front contact, back contact of armature 29 and said armature, wiper 36 and the second bank contact, winding of relay 40 to ground. Relay 40 operates in this circuit in multiple with the switching relay I3 and at armature 4I and its front contact closes the filament battery circuit of the radio set 44. The set is thereby turned on and the program from the desired broadcasting station is received at the loud speaker in the guests room over the above-traced circuit.

Relay 40, in operating, also closes a circuit for the supervisory lamp 43 at armature 42 and its front contact. A lamp, such as 43, is provided at the central switchboard for each of the permanently tuned radio sets, such as 44. Whenever any one of these sets is in use, the associated relay, such as 40 will be energized. If one of the lamps is seldom lighted, the clerk knows that the station to which this associated radio set is tuned is not very popular. The set may then be tuned to a dilerent broadcasting sta.- tion. Thus the permanently tuned radio sets can be tuned to the most popular stations for the radio program service.

The banks of all the selecting switches, such as SS, are multipled together and connected to the permanently tuned radio receiving sets. The loud speakers of all subscribers or guests who are listening to the same radio program are, therefore, in multiple. The volume of reception may be controlled at the loud speaker by means of the variable resistance 2 which is in series with the loud speaker. As long as any guest is listening to a particular one of the permanently tuned radio receiving sets the relay 40 associated with that set will be operated and the filament battery circuit will be closed and the supervisory lamp 43 will be lighted.

When the guest wishes to turn off the selected radio program or to listen to another program he restores the release key R thereby opening the circuit of line relay I of the switch SS. Relay I0 releases and at armature I5 and its front contact opens the circuit of the release relay II. Relay II releases after an interval and at armature I6 and its back contact places a shunt around the winding of switching relay I3 and also completes a homing circuit for the switch SS, as will be described later. At armature 20 and its front contact relay I I opens the circuit of the common relay 40 associated with the receiving set, but this relay is held operated over the wipers of any other switches, such as SS, which may be standing on the second bank contacts. At armature I9 and its front contact relay II opens the rcircuit of the supervisory lamp 9 and at armature I8 it removes battery from release relay II and again prepares a circuit for furnishing battery to relay II through the winding of the rotary magnet 33. Switching relay I3 releases after an interval and at armatures 23 and 26 and their front contacts disconnects the loud speaker from the wipers of the switch.

When armature I6 of relay II closed its back contact a circuit was completed from ground, back contact of armature I6 and said armature, second bank contact engaged by Wiper'31 and said wiper, back contact cf armature 22 and said armature, interrupter springs 34 of the rotary magnet, winding of rotary magnet 33, to battery. 'I'he rotary magnet energizes in this circuit and breaks its own energizing circuit at interrupter springs 34. 'I'he magnet thereupon releases and steps the wipers into engagement with the third bank contacts. It will be noted that the rst nine bank contacts engaged by wiper 31 are multipled together and are supplied with ground from the armature I6 of relay II. The magnet 33 will, therefore, energize each time its interrupter springs 34 are again closed and step the rotary switch into engagement with the tenth bank contacts of the switch. The contacts I0 to 25 of the bank engaged by wiper 31 are multipled together and connected to ground through back contacts on the release relay I I, line relay I0, and switching relay I4. The automatic rotation of the switch will, therefore, continue until wiper 31 is again rotated into engagement with the normal bank contact 39. Since there is no ground present cn contact 39 the switch will come to rest in its normal position. All the apparatus has now been returned to normal and the guest may again operate the switch SS to select any other radio program.

It will now be assumed that the guest wishes to listen to a radio program which is being broadcast by a station which is not listed under the program service, that is, none of the permanently tuned radio receiving sets are tuned to respond to the particular desired station. In this case the guest will consult the list of stations to which the special radio receiving sets may be tuned and will then dial the number corresponding to the desired station. It will be assumed that the desired station corresponds to position 25 of the tuning switch TS. In this case the guest will dial three digits 0, 2 and 5 to tune one of the special radio sets and will then dial an additional digit or digits to adjust the volume to any desired value.

As soon as the release key R is depressed a circuit will be closed for relay I0 of the selecting switch SS which in tum will complete a circuit for the release relay II as previously described. The guest will now dial the digit 0 thereby transmitting ten impulses to the rotary magnet 33 in the manner hereinbefore described. The wipers are thereby rotated into engagement with the tenth bank contacts and the further operation of the switch depends upon the presence or absence of ground upon the tenth bank contact 48 engaged by wiper 36. In case the special radio receiving set accessible from the tenth bank contacts of the switch SS is busy, there will be a ground potential upon bank contact 48 and when the series relay I2 releases at the end of the impulse train a circuit will be closed from ground on contact 48, wiper 36, armature 29 and its back contact, iront contact of armature 20 and said armature, back contact of armature 2| and said armature, interrupter spring 34 of the rotary magnet 33, winding of the rotary magnet, to battery. Rotary magnet 33 thereupon energizes and interrupts its energizing circuit at the interrupter contact 34. The magnet deenergizes and steps the wipers of the switch into engagement with the eleventh bank contacts. If there is ground on the eleventh bank contact engaged by wiper 36 this operation is repeated and the wipers of the switch are stepped into engagement with the twelfth bank contact. During the automatic rotation of the switch over busy bank contacts the ground encountered by wiper 36 also serves to shunt the switching relay I4 so that this relay will not operate until an idle radio set is found. This shunting ground extends over armature 22 and its back contact, wiper 31 of the switch SS, multplied bank contacts I0 to 25, inclusive, contact 25 of the key K, to the upper terminal of switching relay I4. 'I'he lower terminal of the switching relay I4 is grounded by armature I9 of the release relay II.

It will now be assumed that the radio set connected to the tenth bank contacts of the switches, such as SS, is idle and there is no ground potential present on bank contact 48. In this case when relay I2 releases a short interval after the cessation of the impulse train, a circuit is closed for switching relay I4 which extends from ground, armature I9 and its front contact, winding of switching relay I4, contact 25 of key K, tenth bank contact engaged by wiper 31, wiper 31, back contact of armature 22 and said armature, interrupter springs 34, winding of rotary magnet 33, to battery. Switching relay I4 energizes in this circuit and at armature 28 and its back contact opens a point in the homing circuit of the selecting switch SS and at armature 29 and its front contact prepares a locking circuit for itself. At armatures 21 and 30 and their back contacts it disconnects the line relay I0 and at the front contacts of these armatures it switches the line conductors through to wipers 35 and 38 of the selecting switch. Line relay I0 thereupon releases and at armature I and its front contact opens' the circuit of release relay II. After a short interval relay II releases and at armature I1 and its back contact closes a point in the homing circuit of the switch SS, at armature I8 it again prepares its initial energizing circuit, at armature I9 it opens a point in the initial energizing circuit of relay I4 and at armature 28 it opens a point in the automatic hunting circuit of the switch.

Before release relay I I has had time to deenergize, a holding ground will be sent back over conductor 46 and bank contact 48 engaged by wiper 36 to maintain the switching relay I4 in energized position and keep the supervisory lamp 9 lighted. The manner in which this holding ground is sent back to the selecting switch SS will now be described. As soon as switching relay I4 operates and cuts through the line to wipers 35 and 38 of the selecting switch, a circuit is closed for relay (Fig. 2) extending from ground, lower left-hand winding of repeating coil 50, conductor 45, tenth bank contact engaged by wiper 35 and said wiper, front contact of armature 21 and said armature, tip of plug 8, over one conductor of the line and through the inductance coil I at the loud speaker, back over the other conductor of the line to sleeve of plug 8, armature 38 and its front contact, wiper 38 and the tenth bank contact to which it is connected, conductor 41, lower right-hand winding of repeating coil 58, winding of relay 5| to the negative pole of battery 53. Relay 5| energizes in this circuit and at its armature 54 and front contact closes the lament circuit of the impulsing tube 55', thereby lighting the filament by means of the battery 56. The closure of armature 54 and its front contact also closes the circuit from battery 56 over conductors III to |I2 to the laments of all tubes in the radio receiving set RR.

As soon as the filament circuit of tube 55 is closed, plate current starts to ow in this tube and relay 51 is operated in the plate circuit extending from the plate of tube 55, winding of relay 51, conductor I I3, to the positive pole of battery |58. The relay 51 operates in this circuit and at armature 68 and its front contact prepares the release circuit of the register switches T and U, and at armature 59 and its front contact completes a circuit for the release relay 6 I. Relay 6| operates and at armature 61- and its back contact opens a point in the release circuit of the register switches T and U, at armature 64 and its back contacts open points in the release circuits of the volume control switches VI and V2 and at its front contact closes a point in the impulsing circuit to the register and volume control switches, at armature 58 and its front contact closes an additional point in the circuit of lament battery 56, and at armature 63 and its front contact connects ground to the release trunk conductor 46 to serve as a holding ground for the switching relay I4 as hereinbefore described and also to busy the radio receiving set to all other switches, such as SS.

The grid of the impulsing tube 55 is connected to the junction between the winding of relay 5I and the lower-right-hand winding of the repeating coil 50. The resistance of relay 5| is so chosen, and the lament of tube 55 is connected to battery 53 at a point such that normally, with the line circuit extending to the loud speaker closed, the potential on the grid of tube 55 will be positive with respect to the lament to allow plate current to flow and operate relay 51. However, when the line circuit is opened at the dial impulse springs the induced potential in the winding of relay 5I due to the interruption of the current flow results in a high negative potential on the grid of tube 55 thereby stopping the flow of plate current and allowing relay 51 to release.

Examiner This high negative potential on the grid of tube 55 is only momentary each time the dial springs are opened and the relay 51 is thereby momentarily released in accordance with the impulses transmitted from the dial D.

When the dial D is operated in accordance with the next digit 2, relay 51 momentarily deenergizes twice in the above-described manner and thereby transmits two impulses of current from ground, armature 59 and its back contact, armature 64 and its front contact, armature 14 and its back contact, winding of stepping magnet 11 of the tens register switch T, to battery. Relay 68 energizes in multiple with the stepping magnet and at armature 69 and its front contact closes an obvious circuit for relay 1|. Relay 1| operates without effect at this time. Responsive to the two impulses of current, stepping magnet 11 energizes twice and steps the wiper 80 of the tens register switch T into engagement with the second bank contact. This places ground on conductor ||5 which is connected to the second set of ten bank contacts, numbered 2| to 28, of the tens marking bank wiped over by wiper |31 of the tuning switch TS.'

At the end of the impulse train relay 51 remains energized, tllgsby@ 1I to deenergize. en re ay 8 releases it closes a circuit from ground, armature 68 and its back contact, normally closed springs controlled by armature 15 of relay 13, off-normal springs 16 of the tens register switch T, winding of relay 13, to battery. Relay 13 operates and at armature 15 and its front contact closes a locking circuit for itself independent of the back contact of relay 68. At armature 14 and its front contact relay 13 transfers the impulsing circuit to the stepping magnet 86 or the units register switch U. When the next digit 5 is dialled, relay 51 momentarily releases five times thereby sending ve impulses of current to the magnet 86 of the units register switch U over the following circuit: from ground, armature 59 and its back contact, armature 64 and its front contact, armature 14 and its front contact, armature 83 and its back contact, winding of magnet 86 to battery. The stepping magnet 86 is energized five times, thereby stepping the wiper 89 into engagement with the fifth bank contact. Relay 68 energizgsgn multiple with the stepping magnet 86 and at armature 69 and its front contact closes a circuit for relay 1| in the same manner as hereinbefore described. Wiper 89 of the units register switch U connects ground to conductor IIE which is connected in multiple to bank contacts numbered I5, 25, 35, etc. of the units marking bank wiped over by wiper |38 of the tuning switch TS.

A short interval after the cessation of the digit impulses,relay 68 releases and completes a circuit for relay 8| from ground, armature 69 and its back contact, normally closed springs controlled by armature 82 of relay 8|, o-normal contact 85 of the units register switch U, winding of relay 8|, to battery. Relay 8| operates and at armature 82 and its front contact closes a locking circuit for itself independent of the back contact of relay 68. At armature 83 and its front contact it transfers the impulsing circuit to the stepping magnet 95 of the rst volume control switch VI. At armature 84 and its front contact it grounds the start conductor 4 to start the operation of the tuning switch TS to the position which has been marked by the tens and units register switches T and U, respectively.

The guest or subscriber who is tuning the radio set now proceeds to dial one or more digits in order to adjust the volume of the received program to the desired loudness. Before proceeding with the explanation of the adjustment of the volume control, the operation of the tuning switch TS to the position which has been marked by the tens and units register or marking switches T and U will now be explained.

When relay 8| operated at the end of the impulse train which controlled the setting of the units marking switch U and closed its armature 84 a circuit was completed from ground, armature 84 and its front contact, conductor ||4, winding of relay |2| (Fig. 3) to battery. Relay 2| operates and at armature and its front contact closes the output circuit of the radio receiving set RR to the primary windings of the repeating coil 50. At armature |26 and its front contact a circuit is closed from ground, armature |26 and its front contact, normally closed springs controlled by armatures |28 and |30 in multiple, interrupter contacts |36 and |35 of the rotary magnet |33 of the tuning switch TS, resistance |34, winding of relay 24 to battery. Relay |24 operates in this circuit and at armature |32 and its front contact completes a circuit for the rotary magnet |33. Magnet |33 energizes and steps the wipers of the switch into engagement with the next set of bank contacts. At the beginning of the stroke the interrupter contact |36 is opened but this contact is shunted by armature |3| and its front contact and the circuit of relay |24 is thereby maintained closed until the interrupter contact |35 is opened at the end of the stroke or when the magnet 33 has completely operated. The opening of the interrupter contact |35 allows relay |24 to deenergize thereby opening the circuit of the rotary magnet 33 at armature |32. Magnet |33 deenergizes and closes interrupter contact |35 as soon as its armature starts to return to normal. However, the circuit of relay |24 is held open at interrupter contact |36 until the armature of the magnet has reached its normal position, thereby preventing the possibility of relay |24 again energizing and closing the circuit to the magnet before the magnet armature has completely returned to normal and the pawl has engaged the next tooth on the ratchet wheel. As soon as interrupter contact |36 is again closed, relay 24 again energizes and at armature |32 and its front contact completes the energizing circuit for the magnet |33. Magnet |33 again energizes and steps the wipers of the switch into engagement with the next set of bank contacts. The magnet armature opens interrupter contacts |36 and |35, thereby allowing relay |24 to deenergize and open the circuit of the rotary magnet |33. This alternate operation of relay 24 and the rotary magnet |33 continues until both wipers |31 and |38 simultaneously engage grounded bank contacts.

Assuming that the switch starts from the position shown, the alternate operation of relay |24 and the rotary magnet |33 continues in the described manner until the wipers of the switch are stepped into engagement with the eleventh bank contacts corresponding to a dialled number of 2|. As soon as wiper |31 engages the eleventh bank contact a circuit is closed from the grounded conductor 5, eleventh bank contact engaged by wiper |31 and said wiper, upper winding of relay |22, armature |21 and its back contact, winding of the rotary magnet |33, to battery. Relay |22 energizes in this circuit and at armature |28 and its front contact closes a locking circuit over its lower winding, and at armature |21 and its back contact opens its initial energizing circuit. At armature |63 and its front contact, relay |22 prepares a circuit for relay |23. At the normally closed springs controlled by armature I8, one point in the energizing circuit of relay |24 is opened but this circuit is maintained closed at the normally closed springs controlled by armature of relay |23.

The rotary magnet 33 is held energized in the initial energizing circuit of relay |22 until this circuit is opened at armature |21 and its back contact upon the energization of relay |22. The magnet thereupon releases and at its interrupter contacts and |36 again closes the circuit for the stepping relay |24. Relay |24 energizes and closes armature |32 and its front contact thereby again completing a circuit for the rotary magnet. This alternate operation of relay |24 and the rotary magnet |33 continues until wiper |38 engages a grounded bank contact which in this case is the fteenth bank contact or the contact corresponding to a dialled number 25 as indicated by the marking switches T and U. When the wipers are stepped into engagement with this set of bank contacts a circuit is closed from the grounded conductor ||6, the fteenth bank contact engaged by wiper |38 and said wiper, armature |63 and its front contact, upper winding of relay |23, armature |29 and its back contact, winding of rotary magnet |33, to battery. Relay |23 is energized in this circuit and the rotary magnet |33 is held energized. Relay |23 at armature |30 and its front contact completes a locking circuit for itself over its lower winding and at armature |29 and its back contact opens its initial energizing circuit and allows the rotary magnet |33 to deenergize. By opening the normally closed springs controlled by armature |30, relay |23 opens the second point in the energizing circuit of relay |24 and thereby prevents this relay from again energizing and completing the rotary magnet circuit. The switch is thereby brought to rest in the position which has been marked by the tens and units register switches T and U in accordance with the digits dialled by the hotel guest or subscriber who is tuning the special radio set.

Relay |24 is a specially wound relay having only a few turns of a large size wire in order to reduce the impedance in its energizing circuit to a minimum. The resistance |34 is inserted in the energizing circuit in order to reduce the current to such a value that the relay has only suflicent current to energize it with a small margin of safety. 'Thus when the circuit of the relay is closed the current at once goes up to its maximum value and allows the relay to quickly energize. When the circuit of the relay is opened the relay will quickly deenergize since the impedance in the circuit is practically all non-inductive resistance and the inductive kick due to the opening of the circuit is very small. Thus a very fast and efcient operation of the stepping relay |24 is obtained.

As has been previously pointed out the main tuning condensers 2|0, 2|| and 2|! associated with the radio receiving set RR and used for tuning the two radio frequency stages and the detector stage of the receiving set are mounted on the same shaft with the wipers |31 to |42, inclusive, of the tuning switch TS. Thus when the tuning switch was operated and rotated into its position corresponding to the dialled number 25. the tuning condensers 2| 0. 2| I. and 2|2 were Cil rotated so that the associated stages of the receiving set were approximately tuned to respond to the frequency of the desired broadcasting station. The auxiliary condensers, such as |6|, |60 and |59, the construction of which has been previously explained, are connected in multiple with the main tuning condensers 2|0, 2|| and 2|2, respectively, by means of the associated wipers |39, |40 and |4|, respectively. Thus when the tuning switch TS has been rotated into position twenty-five the radio receiving set RR has been tuned to respond to the frequency of the particular desired radio broadcasting station.

After the tens and units register switches T and U have been set in accordance with the. two digits dialled by the guest or subscriber who is tuning the radio set, an additional digit is dialled to set the rst of the Volume control switches VI in order to connect up the antenna 08 to the radio receiving set. Any digit may be dialled for the initial volume adjustment, the digit 0 giving the loudest volume. It will be assumed in this case that the digit 0 is the first digit dialled for the volume adjustment. When the circuit of relay 5| is interrupted ten times in accordance with the digit 0 the relay 51 releases in accordance with the impulses received and sends ten impulses to the stepping magnet 95 of the first volume control switch VI over the following circuit: from ground, armature 59 and its back contact, armature 64 and its front contact, armature 14 and its front contact, armature 83 and its front contact, armature 9| and its back contact, winding of magnet 95, to battery. Relay 58 energizes at the rst impulse of the series and remains energized throughout the series. Relay 68 at armature 10 and its back contact opens a point in the release circuit of the register switches T and U to prevent the possibility of these switches releasing during the impulsing. At armature 59 and its front contact relay 68 closes an obvious circuit for relay 1| which operates and closes its armature 12 and front contact without elect at this time.

A short interval after the cessation of the impulse series relay 68 releases and at armature 69 and its front contact opens the circuit of relay 1 After a short interval relay 1| releases and at armature. 12 and its back contact completes a circuit foI relay 90 which extends from ground. armature` 59 and its back contact, armature 12 and its back contact, normally closed contacts controlled by armature 92 of relay 90, orf-normal contacts 94 of the volume control switch V|, winding of relay 90 to battery. Relay 90 operates and at armature 92 and its front contact completes a locking circuit for itself independent of relays 68 and 1|. At armatures 9| and its front contact relay 90 extends the impulsing circuit to the stepping magnet |04 of, the second volume control switch V2. At armature 93 and its front contact relay 90 prepares a release circuit for the rst volume control switch VI.

In response to the receipt of the ten impulses by the stepping magnet 95, the wiper 98 of switch Vl is stepped into engagement with its tenth bank contact, thereby connecting the aerial |08 to conductor ||1 extending to terminal ||8 of the potentiometer |44. The bank contacts engaged by wiper |42 of the tuning switch TS are cross connected to various points in the resistance |43, depending upon the loudness with which the Various stations may be received by the receiving set RR. For example, the bank contacts |64 on which wiper |42 is resting after the tuning switch has rotated to the selected position in the assumed case, is connected to the left-hand terminal of the resistance |43 which is the point closest to the negative terminal of the battery |55 which is used as a C biasing battery for the antenna connecting tube |50 of the radio receiving set. The signals from the broadcasting station which correspond to this particular position of the tuning switch are very strong and this particular bank contact |64 has, therefore, been connected at the point of the resistance |43 nearest to the biasing C battery in order to obtain the minimum volume of reception from this particular broadcasting station. The connections between the bank contacts of wiper |42 and the terminals of the resistance 43 are made in such a manner that with the antenna connected to any particular point of the potentiometer |44, the signals from each of the broadcasting stations will come in with approximately the same loudness.

When the digit 0 was dialled the antenna |08 was connected to terminal ||8 of the potentiometer |44 over conductor 1. With the antenna connected to this point the signals incoming over the antenna are equally divided between resistances |44 and |43 and the signal strength passing through resistance |43 is a maximum. The radio receiving set will therefore, be adjusted for the maximum volume.

The radio receiving set RR has now been tuned il to respond to the desired broadcasting station and the antenna |08 has been connected up so that the guest or subscriber will hear the desired program from the loud speaker LS located in his room. The output of the last amplifying tube |45 5' of the radio receiving set passes through the windings of the repeating coil 50, over line conductors 45 and 41, Wipers 35 and 38 of the selecting switch SS, armatures 21 and 30 and their front contacts, tip and sleeve of the plug 8 and the associated springs of jack 1, wall jack 5, sleeve and tip of plug 5, springs of the release and special releae keys R and SR, springs of dial D, and condenser 3 and resistance 2, to the loud speaker LS. In case the program which is being received is too loud the subscriber will proceed to dial another digit in order to re-adjust the volume of reception. In this case it will be assumed that the digit 5 is dialled. Relay 51 follows the interruptions of dial D and transmits ve impulses of current to the rotary magnet |04 of the second volume control switch V2 over the following circuit: from ground, armature 59 and its back contact, armature B4 and its front contact, armature 14 and its front contact, armature 83 and its front contact, armature 9| and its front contact. armature |00 and its back contact, winding of magnet |04, to battery. Relay 68 is energized iti multiple with the rotary magnet |04 of switch V2 and at armature 69 and its front contact completes a circuit for relay 1| which also energizes.

Rotary magnet |04 responds to the received impulses and rotates wiper |01 into engagement with the fifth bank contact. At the end of the impulse train relay 68 releases after a short interval and opens the circuit of relay 1|. Relay 1| is also slow-to-release and before it retracts its armature 12, a circuit is closed from ground, armature 69 and its back contact, armature 12 and its front contact, front contact of `armature 93 and said armature, off-normal contacts 91 of switch Vl, winding of release magnet 95, to battery. Release magnet 9S energizes in this circuit and restores the first volume control switch V| to normal, thereby opening the off-normal contacts 94 and 91. The opening of contact 91 opens the circuit of the release magnet 96 and the opening of contact 94 opens the circuit of relay 90 allowing this relay to release. Relay in releasing at armature 92 and its front contact opens a point in its, locking circuit and at the normally closed springs controlled by armature 92 again closes a point in the initial energizing circuit of relay 90. At armature 9| and its back contact relay 90 again transfers the impulsing circuit to the rotary magnet 95 of switch VI. Relay 1| releases after an interval and at armature 12 and its back contact closes a circuit from ground, armature 6 9 and its back contact, armature 12 and its back contact, normally closed springs controlled by armature |0| of relay 99, olf-normal contacts |03, winding of relay 99, to battery. Relay 99 operates and at armature |0| and its front contact closes a locking circuit for itself. At armature |02 and ita front contact it prepares a point in the circuit of the release magnet of switch V2.

Wiper |01 of switch V2 is now in engagement with the fth bank contact and connects the antenna |08 to terminal ||9 of the potentiometer |44. The incoming signals are now divided so that a smaller portion of the signal passes through the right-hand portion of the resistance |44 and the resistance |43. The strength of the signal passing through resistance |43 has been decreased and thereby the input to the antenna connecting tube |50 is proportionally decreased and the volume of the set or loudness at which the program is received at the loud speaker LS has also been decreased.

It will now be assumed that after the second adjustment of the volume has been made it is discovered that the program does not corne in with suicient strength and more volume is desired. In this case the guest or subscriber listening to the program may operate the dial in accordance withthe digit 7. Relay 51 follows the interruptions of the dial springs and transmits seven impulses in turn from ground, armature 59 and its back contact, armature 64 and its front contact, armature 14 and its front contact, armature 83 and its front contact, armature 9| and its back contact, winding of rotary magnet 95 of switch VI, to battery. The rst impulse operates relay 68 which in turn closes a circuit for relay 1| in the same manner as hereinbefore described. Magnet 95 rotates wiper 98 of switch VI into engagement with the seventh bank contact. A short time after the cessation of the impulse train, relay 68 releases and at armature 69 and its back contact closes a circuit from ground, armature 69 and back contact, armature 12 and its front contact, front contact of armature |02 and said armature, olf-normal springs |06 of switch V2, winding of release magnet |05, to battery. Release magnet |05 energizes and returns the second volume control switch V2 to its normal position, thereby opening the off-normal contacts |03 and |06. The opening of contact |06 opens the circuit of the release magnet 05 and the opening of contacts |03 opens the locking circuit of relay 99 which thereupon releases.

After a short interval relay 1| releases and at armature 12 and its back contact completes a circuit from ground, armature 69 and its back contact, armature` 12 and its back contact, normally closed springs controlled by armature 92 of relay 90, off-normal springs 94 of switch Vl, winding of relay 90, to battery. Relay 90 operates in this circuit and at armature 92 and its front contact completes a locking circuit for itself extending over the off-normal contact 94. At armature 9| and its front contact relay 90 transfers the impulsing circuit to the stepping magnet |04 of the volume control switch V2. At armature 93 and its front contact it again prepares a release circuit for the release magnet 96 of switch V|.

The rotation of wiper 98 into engagement with the seventh bank contact connects the antenna |08 to terminal |65 of the potentiometer |44. Thus a greater portion of the incoming signals pass through the resistance I 43 and a corresponding increase in volume or loudness of the received program results.

From the foregoing it is seen that any number of digits may be dialled in order to adjust the volume or loudness of the received program to any desired value. The first digit operates the switch VI, the second operates the switch V2 and releases the switch VI, the third operates the switch V| and releases switch V2, and it is therefore seen that any number of digits may be dialled, every second digit releasing the switch V2 and operating VI and the alternate digits releasing the switch V| and operating switch V2. After the volume has been adjusted by means of the switch VI and V2 as described above a still ner adjustment of the volume to the exact desired loudness may be made by means of the variable resistance 2 at the loud speaker.

V'I'he operation of the radio receiving set RR will not be explained in detail since this receiving set may be any one of a number of well known makes and since the operation of such receiving sets are well known in the art. A volume control key |20 is'mounted on the central switchboard in the hotel or apartment house oflce and when operated connects ground to the winding of all relays, such as |5| one of these relays being provided for each radio receiving set. In order to provide against any of the guests or subscribers of the service tuning in a radio set and adjusting the volume so loud that other guests of the hotel will be disturbed late at night, the clerk on duty at eleven or twelve oclock or any other desired hour may operate the key |20 thereby operating all relays, such as |5|, in multiple. The operation of relay |5| at armature |52 disconnects the maximum B battery voltage from the two amplifying stages |45 and |46, and at its front contact connects the plate circuits of these amplifying tubes to the positive pole of battery |56, thereby reducing the plate voltage of these amplifying stages and limiting the maximum volume output of the radio receiving set. At armature |53 the negative C bias comprising batteries |54 and |55 is removed from the grid of the two amplifying stages |45 and |46 and at the front contact of this armature these grid circuits are connected direct to one terminal of the filament battery. With the relays, such as |5|, operated the maximum volume output of the radio receiving sets are limited to such a value that the adjustment of the volume by means of the volume control switches to its maximum will not allow the program to be received with such loudness as to cause a nusiance.

As previously pointed out, the cross connections between the bank of the tuning switch TS wiped over by wiper |42 and the various points along the resistance |43 are made in such a manner that with the antenna connected to any particular point of the potentiometer |44, all stations will be received with approximately the same volume. When a guest has finally adjusted release key R and attempt to operate the selecting switch SS before this switch has returned to normal, line relay I will operate and at armature I and its front contact close a point in the circuit of release relay II but the other terminal of release relay II is notv connected to battery until wiper 31 has reached its normal bank contact 39. 'Ihe self interrupting circuit of the rotary magnet 33 is opened when the switch reaches its normal position and all of the apparatus has now been restored to normal.

The management of the hotel or apartment house may desire to charge for the radio service and in this case it may be desirable to charge a different rate for the program service alone, for service which gives only access to the special radio receiving sets which may be controlled by the subscriber, and for service which includes both the permanently tuned radio program service and which also gives access to the special radio receiving sets which may be controlled by the subscriber. In order to discriminate between these services a key K is provided for each of the selecting switches, such as SS, and this key is mounted on the central switchboard with the connecting plug of the associated switch SS. In case a subscriber wishes only the radio program service, the key K is operated to the right thereby opening the contact 25. The guest or subscriber may now operate the selecting switch SS to select any one of the permanently tuned radio sets and the operation will be the same as previously described. However, should the guest attempt to dial the digit 0 in order to select one of the special radio receiving sets, such as RR, the switch SS will automatically hunt for an idle trunk in the same manner as previously described, but when an idle trunk to a special radio receiving set is found the switching relay Il cannot operate since its circuit is opened at contact 25 of key K. The switch SS will, therefore, remain in this position until the subscriber again opens the release key R and allows the switch to restore to normal in the previously described manner.

In case the subscriber desires access only to a special radio receiving set and does not wish the radio program service, the key K is operated to its left-hand position thereby opening the contact 24. The subscriber may now dial the digit 0 and select an idle special radio receiving set in the same manner as previously described, but should he attempt to dial any digit from 1 to 9 in order to select one of the permanently tuned radio receiving sets, the selecting switch SS will respond to the digit but the switching relay I3 cannot operate at the end of the impulse train, since its circuit is opened at contact 24 of the key K. The subscribers line will, therefore, not be switched through to the permanently tuned radio receiving sets and he will not have access to this service. In case the subscriber desires both of these services the key K is left in its normal position and contacts 24 and 25 remain closed so that either the switching relay I3 or the switching relay I 4 may be operated to switch the subscribers line through condensers 3| and 32 to the permanently tuned radio receiving sets or directly through to the impulsing relay 5I associated with one of the special radio sets.

Although a particular embodiment of the invention has been illustrated and described in the foregoing specification, it will be apparent that a large number of modifications may be made by those skilled in the art without departing from the spirit of the invention.

Having described the invention, what is thought to be new and what is desired to have protected by Letters Patent will be pointed out in the appended claims.

What is claimed is:

1. In a radio service system, a plurality of subscribers stations each equipped with a loud speaker and a dial, a plurality of permanently tuned radio receiving sets, a plurality of tunable radio receiving sets, and means responsive to the operation of the dial at one of said stations and dependent upon the value of the digit dialled for connecting the loud speaker at that station to any desired one of said permanently tuned radio sets or to an idle one of said tunable radio sets, and for tuning one of said tunable sets.

2. In a radio service system, a plurality of subscribers stations each equipped with a loud speaker and a dial, a plurality of permanently tuned radio receiving sets, a plurality of tunable radio receiving sets, means responsive to the operation of the dial at one of said stations and dependent upon the value of the digit dialled for connecting the loud speaker at that station to any desired one of said permanently tuned radio sets or to an idle one of said tunable radio sets, means operated by said dial to tune said tunable radio sets, and means for preventing the connection of said loud speaker to said permanently tuned radio sets or to said tunable radio sets as desired.

3. In a radio service system, a plurality of subseribers stations each equipped with a loud speaker and a dial, a plurality of permanently tuned radio receiving sets, a plurality of tunable radio receiving sets, means responsive to the operation of the dial at one of said stations and dependent upon the value of the digit dialled for connecting the loud speaker at that station to any desired one of said permanently tuned radio sets or to an idle one of said tunable radio sets, and means controlled by said dial and operative when an idle one of said tunable radio sets is connected with for tuning the selected radio set to respond to any desired broadcasting station.

4. In a radio service system, a subscribers station equipped with a dial and a 19nd speaker, a plurality of radio receiving sets, means responsive to the dialling of a particular digit for connecting said loud speaker to an idle one of said radio sets, means responsive to the dialling of additional digits for tuning said radio set to respond to any desired broadcasting station, and means responsive to further operation of said dial for thereafter adjusting the volume of the received program.

5. In a radio service system, a radio receiving set, a remote control station equipped with a dial, a plurality of register switches for registering the dialled digits which designate the desired broadcasting station, a tuning switch, means for operating said tuning switch to the position designated by the setting of said register switches, means in said switch for tuning said radio set to respond to the desired broadcasting station, and means controlled by said dial for thereafter adjusting the volume of reception.

6. In a radio service system, a radio receiving set, a remote control station equipped with a dial, means responsive to the dialling of a predetermined number for tuning said radio set to respond to the desired broadcasting station, two volume control switches, means in each switch for controlling the output volume of said receiving set, means for operating the rst of said switches responsive to the dialling of an addi- 2599.. RBD" tional digit to adjust the volume at a particular value depending upon the value of the digit dialled, and means responsive to the dialling of a further digit for operating the second of said switches and releasing the first to adjust the volume at a diierent value depending upon the value of the further digit dialled.

7. In a radio service system, a radio receiving set, a remote control station equipped with a dial, a tuning switch, two marking switches, means responsive to the operation of said marking switches in accordance with two digits dialled for causing said tuning switch to position itself in a position determined by the setting ol' said marking switches, means in said switch for tuning said radio set to respond Vto the desired broadcasting station, two volume control switches, means in each volume control switch for controlling the output volume of said receiving set means for alternately operating said volume control switches in accordance with additional digits dialled, the operation of one of said volume control switches releasing the other, and means controlled from said control station for releasing said marking switches without releasing the operated volume control switch.

8. In a radio service system, a radio receiving set, a remote control station equipped with a dial, a plurality of marking switches, means responsive to the operation of said marking switches under control of said dial for tuning the radio set to respond to the desired broadcasting station, volume control switches operated under control of said dial, means controlled by said volume control switches for controlling the output volume of said receiving set, and means controlled from said control station for releasing and resetting said marking switches to tune said radio set to respond to a diierent broadcasting station without releasing said volume control switches.

9. In a radio service system, a radio receiving set, a remote control station equipped with a dial, a plurality of marking switches, a plurality of volume control switches, means in each volume control switch for adjusting the output volume of said receiving set, means responsive to the operation of said marking switches in accordance with dialled digits for tuning said radio set to respond to the desired broadcasting station, means responsive to additional digits dialled for operating said volume control switches to adjust the volume of said set to any desired value, and means controlled from said remote control station for releasing all of said switches or for releasing only said marking switches.

10. In combination, a main variable tuning condenser for a radio receiving set, circuit means for selecting and then remotely controlling the adjustment of said condenser to approximately tune said radio set to a particular wave length, a plurality of auxiliary tuning condensers, normally open circuit connections between said main and said auxaliary condensers, and selecting means controlled by said circuit means simultaneously with said main tuning condenser for selecting and closing a circuit connection for a particular one of said auxiliary condensers to exactly tune said radio set to the particular Wave length.

11. In combination with a radio receiving set, a plurality of main variable tuning condensers, a control circuit, remotely controlled means for selecting and simultaneously adjusting .all of said condensers over said control circuit to approximately tune said radio set to a desired wave length, a plurality of auxiliary condensers, normally open circuit connections between said main and auxiliary condensers, and a selector simultaneously operated with said main tuning condensers for selecting a particular one of said auxiliary condensers and for closing said circuit connections, the selected auxiliary condensers cooperating with said main condensers to exactly tune said radio set to the desired wave length.

l2. In combination, a radio receiving set, a control circuit, a step-by-step rotary switch, a plurality of tuning condensers having their movable elements mounted on the shaft of said switch, circuit means for selecting-and operating said switch over said control circuit to any desired position thereby adjusting said condensers to approximately tune said radio set to respond to the desired broadcasting station, a wiper and bank for each tuning condenser, circuit connections between said condensers, said wipers and banks, and means including said wipers and banks and controlled over said circuit connections for exactly tuning said radio set to respond to the selected broadcasting station.

13. In combination, a radio receiving set, a rotary tuning switch, a control circuit remotely controlled means controlled over said control circuit for operating said switch to any desired position, a plurality of multi-plate tuning condensers on said switch for tuning said radio set consequent to the rotation of said switch, a wiper and bank for each of said tuning condensers, and an auxiliary condenser connected to each contact of said banks, certain of said auxiliary condensers being connected in multiple with said tuning condensers in each position of said switch to provide sharp tuning of said radio set to the selected broadcasting station.

14. In a homing ty rotary switch having a plurality of wipers and banks, a line relay, a release relay, an operating magnet, an impulsing circuit to said magnet including contacts on said line and release relays, self-interrupting homing circuits for said magnet including a wiper of said switch and back contacts on said release relay, and an energizing circuit for said release relay completed by the operation of said line relay and including said wiper and the associated normal position bank contact.

15. In a homing type rotary switch having a plurality of wipers and banks, an operating magnet, a release relay, an impulsing circuit for sad magnet including front contacts on said release relay, self-interrupting restoring circuits for said magnet including a wiper of said switch and back contacts on said release relay, and an operating circuit for said release relay including said magnet and said wiper and its associated normal position bank contact, whereby said release relay is prevented from operating to close said impulsing circuit until said switch has been restored to its normal position.

16. In combination, a single-motion rotary switch controlled over an incoming line, two groups of trunks accessible to said switch, means responsive to received digit impulses for operating said switch to connect with a desired trunk in the first group or to select an idle trunk in the second group dependent upon the value of the digit dialled, a pair of condensers in said switch, means responsive to the seizure of the desired trunk in the first group for connecting the incoming line to the seized trunk through said condensers, and means responsive to the seizure of an idle trunk in said second group for directly Kammer connecting the incoming line to the seized trunk independently of said condensers.

17. In combination, a. control circuit terminating in a relay and a battery, a vacuum tube having a grid circuit including said relay and battery, a plurality of switches, means for interrupting said control circuit in accordance with digit impulses, means controlled by said tube for repeating said impulses to operate said switches, and means responsive' to a decrease in current in said control circuit for releasing only certain of said switches while maintaining the remainder operated.

18. In combination, an incoming loop circuit terminating in a relay and a battery, a vacuum tube, a grid circuit for said tube including said relay and battery, a plate relay for said tube, means for intermittently opening said loop circuit in accordance with digit impulses whereby said tube brings about corresponding deenergizations of said plate relay to repeat said impulses, two release circuits, means for opening said loop circuit to close the first release circuit responsive to a continued deenergization of said plate relay, and means for inserting a resistance in said loop circuit to close the second release circuit, the decreased current due to said resistance allowing said rst relay'to release while said plate relay remains energized.

19. In combination, an incoming control circuit terminating in a relay and a battery, a vacuum tube having a grid circuit including said relay and battery, a plate relay for said tube, means for intermittently opening said control circuit in accordance with digit impulses whereby each interruption of current through said rst relay places a negative potential on the grid of said tube to momentarily release said plate relay, means controlled by said plate relay for repeating said impulses, a plurality of switches operated by the repeated impulses, a release circuit for all of said switches, a second release circuit for only certain of said switches, means responsive to a continued deenergization of said plate relay for completing said rst release circuit, and means for inserting a resistance in said control circuit whereby the reduced current releases said rst relay while said plate relay is maintained operated, thereby completing said second release circuit.

20. In a radio service system, a plurality of subscribers stations, a plurality of permanently tuned radio receiving sets, a plurality of tunable radio receiving sets, a selecting switch individual to each of said subscribers stations, each switch having access to all of said radio sets, and means controlled from one of said stations for operating the associated switch to connect said station with any desired one of said permanently tuned radio sets or to an idle one of said tunable radio sets, and for tuning said tunable radio sets.

21. In a hotel radio service system, a plurality of permanently tuned radio receiving sets, a plurality of tunable radio receiving sets, a control board, a plurality of link circuits terminating at said control board, each link circuit including a plurality of wipers, a plurality of subscribers lines terminating at said board, manually operated means whereby any of said link circuits may be connected to any subscribers line, and means controlled over a subscribers line for operating the Wipers of the connected link circuit to connect the subscribers line with any desired one of said permanently tuned radio sets or to an idle one of said tunable radio sets, and for tuning said tunable radio sets.

22. In a remote control radio system, a subscribers station, a calling device at said station, a plurality of radio receivers, means responsive to a digit dialled by said calling device at said station for automatically selecting an idle one of said receivers, means responsive to additional digits dialled by the calling device for tuning the selected receiver to any desired broadcasting station, and means responsive to any number of further digits dialled by said calling device for adjusting the output volume of said receiver, each digit adjusting the volume to a predetermined value dependent upon the value of the digit dialled.

23. In a remote control radio system, a subscribers station, a calling device at said station, a plurality of radio receivers, means controlled from' said station responsive to dialled digits by said calling device for selecting an idle receiver, means controlled by said calling device for tuning the selected receiver to any desired broadcasting station, means responsive to additional digits dialled by said calling device for adjusting the volume of the output of said receiver to any desired value, and means controlled by said calling device for retuningsaid receiver to a second broadcasting station while maintaining said volume control means in its last operated position so that the second station is received at the volume to which the set was adjusted to receive the first station.

24. In a radio service system, a plurality of radio receiving sets, an impulse sending device, means responsive to a series of impulses from said device for selecting an idle one of said sets, means responsive to additional series of impulses from said device for tuning the selected set, means responsive to said additional series of impulses for adjusting the volume of this set, and means responsive to a further series of impulses from said device for changing the volume adjustment.

25. In combination, a radio receiving set including a tube, a plurality of adjustable condensers having their movable elements mounted on the same shaft, a wiper mounted on said shaft and connected to the grid of said tube, a biasing battery, a resistance, an antenna connected to the lament of said tube in series with said resistance and said battery, a plurality of bank contacts and diierent points along said resistance so that the amount of resistance included in the grid circuit of said tube when the shaft is rotated to tune the receiving set will maintain the output volume of said set at the same level irrespective of the differences in signal strength 'of the broadcasting stations.

HERBERT H. HULSE. JOHN I. BELLAMY. RODNEY G. RICHARDSON. LAURENCE J. LESH. 

